Study on Cracking of Anchor Structure due to Reinforcement Corrosion

Abstract:

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Reinforcement corrosion is one of the main causes for the deterioration of reinforcement concrete structure. And it seriously affected mechanical properties of anchor structure system of underground engineering under complicated erosion environment. Based on elastic theory and assumption of maximum tensile-stress failure criterion, together with construction process of anchor structure and rust expansion critical process, reinforcement rust expansion mechanical model of anchor structure system was simplified. Elastic criterion of different initial cracking mode was rewarded under different stress ratios. According to analysis of critical cracking mode of different medium, cracking order of mortar and surrounding rock depended on their material parameters, in-situ stress and thickness of mortar cover. Critical cracking conditions of different medium without effect of in-situ stress was rewarded. The result provides a useful reference for analysis of mechanical deterioration mechanism of anchor structure and design of support structure of underground engineering.

Abstract: In this study, an experiment program is presented to study the bonding mechanism
between corroded bolts and grout and in particular the influence on bonding behavior in terms of
different corrosion sections along anchor. With respect to four groups of manufactured bolt
specimens, the noncorroded and the corroded, respectively, on the front, middle and rear section
along anchor, a pullout test is conducted to reveal the relationship between load and loading-end
slip and to investigate the bond-stress distribution characterization along full anchor. Experimental
results show that corrosion product, acting as lubricating effect at the interface between bolts and
grout, can result in the degradation of bonding mechanical behavior. Meanwhile, corrosion on
different sections along anchor has a different effect on the anchorage capacity of bolts. Especially,
corrosion on the front section induces the greatest decrease of anchorage capacity of bolts. Thus, it
is concluded that the front section along anchor is the key region affecting the bonding mechanical
behavior between bolts and grout.

Abstract: Initial stress anchor wire anchoring technology has the merits of fast speed, small perturbation and economic when healing unstable rock side slope. Choosing the spacing, position, angle of reinforcement anchor wire plays a vital role in reinforcement stability and economy. The landslide of an open pit was elected as project background in this paper. Operation model was set up by Lagrange arithmetic which analyzed the reinforcement mechanic and broken pattern of anchor wire. And it defined that the optima spacing is 8m. The anchor wire reinforcement angle and institution position research were researched by using limit balance theory. The optimum design angle obtained is -20°~20°, and the optimum institution position is in the range of 1/5~1/2 of the lower reinforcement side slope height.

Abstract: The tunnel excavation and support process were simulated by using ANYSY. Firstly, support effects were studied on different modes of support. Secondly, numerical simulation was realized by using the function of APDL parametric design language in ANSYS. By discussing the different support effects which were arrived through changing support parameters and geometric parameters, conclusions and recommendations were put forward. At last, it could be clearly seen that the simulation results were in good agreement with the monitoring records.

Abstract: Chloride-induced steel corrosion is one of the major deterioration problems for steel reinforced concrete structures. Its effects on RC structures include cracking of the concrete cover, reduction and eventually loss of bond between concrete and corroding reinforcement, and reduction of cross-sectional area of reinforcing steel. The accumulated corrosion products on the bar surface cause longitudinal cracking of the concrete cover. Loss of concrete cover leads to reduction in bond strength at the interfacial zone between the two materials. In addition, the deterioration of the ribs of the deformed bars causes a significant reduction of the interlocking forces between the ribs of the bars and the surrounding concrete keys. This deteriorates the primary mechanism of the bond strength between deformed bars and concrete, and hence, the bond strength decreases significantly. In this paper the effect of reinforcement corrosion on the bond strength between reinforcement and concrete was investigated for different corrosion levels. The effect of corrosion was simulated by the nonlinear numerical analysis with the FEM program using the 3D models.